now a lot of investors are investing in bitcoin, therefore bitcoin has increased very rapidly, if bitcoin decreased what should be done?, whether the investors will lose? 
you dont have to do anything, just dont panic. most peoples get panicked when the price down, and they want to cut their losses by selling it.
that is panic sell. from my opinion, panic sell wont do any good. it is not change the fact that you already loss.
The crypto market react so much on news, some make hype and some really are affected with the FUD, that's why it's a high risk
because some does really panic easily since bitcoin is still not a stable investment.